Tropical Storm ALVIN (Text)

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TROPICAL STORM ALVIN DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL EP012013
200 PM PDT THU MAY 16 2013
THERE IS SOME QUESTION WHETHER ALVIN STILL HAS A CLOSED LOW-LEVEL
CIRCULATION. THE STORM IS STILL FULLY EMBEDDED WITHIN THE ITCZ AND
IS SOMEWHAT DIFFICULT TO DISTINGUISH FROM ANOTHER CLUSTER OF DEEP
CONVECTION A FEW HUNDRED NAUTICAL MILES TO ITS SOUTHWEST. SINCE
THE SATELLITE APPEARANCE HAS WORSENED SINCE THIS MORNING...AND
DVORAK INTENSITY ESTIMATES ARE T3.0 FROM TAFB AND T2.5 FROM
SAB...THE INITIAL INTENSITY IS LOWERED TO 40 KT. THIS COULD BE
OVERLY GENEROUS.
ALVIN ACCELERATED A BIT THIS MORNING BUT HAS AN AVERAGE MOTION OF
285/10 KT. SINCE THE STORM HAS BEEN UNABLE TO DETACH ITSELF FROM
THE ITCZ...IT IS DOUBTFUL THAT ALVIN WILL MAKE MUCH NORTHWARD
PROGRESS. IN DIRECT CONTRAST TO YESTERDAY...THE TRACK GUIDANCE IS
NOW IN FULL AGREEMENT ON A GENERAL WEST-NORTHWESTWARD MOTION DURING
THE 5-DAY FORECAST PERIOD WITH VERY LITTLE SPREAD AMONG THE
INDIVIDUAL MODELS. THE UPDATED NHC TRACK FORECAST IS ESSENTIALLY
UNCHANGED FROM THE PREVIOUS ONE.
THE UW-CIMSS SHEAR ANALYSIS INDICATES THAT ALVIN IS BEING AFFECTED
BY 20-25 KT OF WESTERLY SHEAR...AND IT IS UNLIKELY THAT THE SHEAR
WILL ABATE DURING THE NEXT FEW DAYS. THE CURRENT STRUCTURE OF THE
STORM DOES NOT SUGGEST THAT STRENGTHENING IS LIKELY...AND THE NEW
NHC INTENSITY FORECAST HAS AGAIN BEEN LOWERED. THIS FORECAST
ESSENTIALLY FOLLOWS THE SHIPS...LGEM...AND FSU SUPERENSEMBLE MODELS.
ALVIN IS FORECAST TO DEGENERATE TO A REMNANT LOW IN ABOUT 4 DAYS.
HOWEVER...ADVISORIES COULD BE TERMINATED AT ANY TIME IF IT IS
DETERMINED THAT THERE IS NO LONGER A CLOSED CIRCULATION.
FORECAST POSITIONS AND MAX WINDS
INIT 16/2100Z 9.5N 109.1W 40 KT 45 MPH
12H 17/0600Z 9.8N 110.5W 40 KT 45 MPH
24H 17/1800Z 10.8N 112.0W 35 KT 40 MPH
36H 18/0600Z 11.5N 113.3W 35 KT 40 MPH
48H 18/1800Z 12.0N 114.7W 35 KT 40 MPH
72H 19/1800Z 13.0N 117.5W 30 KT 35 MPH
96H 20/1800Z 13.0N 120.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 21/1800Z 13.0N 122.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
$$
FORECASTER BERG
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